In contrast to most other nations, the United States has a unique tax system that taxes all of its people on their worldwide income, wherever they reside. Most other countries only tax those who live there or those whose money is earned there. However, the US tax system compels all nationals, even expatriates, who earn at least $12,550 globally or $400 from self-employment, or just $5 if they are married to a non-US taxpayer, to submit US taxes. Sadly, this need is unaffected by the tax treaties that the US has with other nations. If you are worried and tensed about how to file Federal tax for non residents, then, one name you can definitely trust is USA Expat Taxes.